1. Field of the Invention
The present invention relates to a developing device used to develop an electrostatic latent image formed on an image-carrying member in an image forming apparatus such as a copier, printer and the like. The present invention specifically relates to a developing device provided with a magnet member having a plurality of magnetic poles on the interior side of a developing sleeve that rotates to transport developer to a developing region confronting said image-carrying member, and which controls the amount of developer transported to said developing region via said developing sleeve by means of a regulating member disposed so as to confront said developing sleeve through a predetermined gap.
2. Description of the Related Art
Conventionally, in image forming apparatuses such as copiers, printers and the like, various developing devices have been used to develop latent images formed on an image-carrying member.
FIG. 1 shows an example of such a developing device. A magnet member 12 having a plurality of magnetic poles N and S is provided within a developing sleeve 11 disposed so as to confront an image-carrying member 1. Developer is maintained on the surface of developing sleeve 11 via the magnetic force of the magnet member 12. Developer is transported in a magnetic brush state to the image-carrying member 1 by means of the rotation of the developing sleeve 11. Developer transported to a developing region opposite the image-carrying member is regulated by a regulating member 13 provided so as to confront the developing sleeve 11 with a predetermined spacing therebetween. Developing sleeve 11 transports a suitable quantity of developer in a magnetic brush state to the developing region, and brings the developer into contact with the image-carrying member. An electrostatic latent image formed on the surface of the image-carrying member is developed, thereby.
When accomplishing developing through contact of a magnetic brush with the image-carrying member 1, however, the toner supplied to the image-carrying member is swept by the magnetic brush, thereby producing streak-like noise in the formed image which disturbs the image.
In recent years, there have been investigations into developing by narrowing the gap Db between the developing sleeve 11 and the regulating member to reduce the amount of developer transported to the developing region by the developing sleeve 11, and using the action of an alternating electric field in the developing region wherein the developing sleeve 11 confronts the image-carrying member 1 so as to accomplish developing without contact between the developer and the image-carrying member.
When the gap Db between the developing sleeve 11 and regulating member 13 is narrowed, however, irregular amounts of developer are transported to the developing region by the developing sleeve 11. Furthermore, foreign matter contained within the developing device as well as flocculant such as flocculated developer and the like within the developing device may accumulate between the developing sleeve 11 and the regulating member 13 so as to prevent developer from being transported by the developing sleeve 11 and produce undeveloped image areas such as white streaks and the like in the formed images.
A regulating member 13 formed of magnetic material magnetically binds the developer to the regulating member 13. Therefore, a suitable amount of developer is transported by developing sleeve 11 to the image-carrying member 1 even when the gap Db is increased between the developing sleeve 11 and regulating member 13.
Even when the regulating member 13 is formed as a magnet member, however, there is variation in the positional relationship between the regulating member 13 and the magnetic pole S of the magnet member 12 confronting the regulating member 13 due to the positioning of the magnet member 12 in the interior side of the developing sleeve 11. Furthermore, when there is variation in the gap Db between the developing sleeve 11 and the regulating member 13, there is great fluctuation in the amount of developer transported by the developing sleeve 11 to image-carrying member 1. Suitable developing cannot be accomplished when too much or too little developer is transported to the image-carrying member 1, such that images having stable density and without image noise cannot be obtained.